JP2012202265A - Exhaust gas recirculation device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas recirculation device of an internal combustion engine at low cost, capable of striking a balance between the prevention of main components from degradation caused by condensed water and the securement of an exhaust purification performance.SOLUTION: An exhaust gas recirculation device of the internal combustion engine is installed in an engine 10 having a DPF unit 45 in a midstream of an exhaust pipe 42 forming an exhaust gas passage 42w. The device includes an LPL-EGR pipe 71 for circulating exhaust gas purified by the DPF unit 45 from the exhaust gas passage 42w side to an intake passage 32w side, a foreign matter capturing filter 80 arranged adjacent to an upstream end 71u of the LPL-EGR pipe 71 so as to prevent entering of foreign matters into the pipe 71 and protruded from an inner wall surface 51a of a cylindrical case part 51 of the DPF unit 45 into the exhaust gas passage 42w, and a water absorbing member 86 provided in the exhaust gas passage 42w and adjacent to the foreign matter capturing filter 80.

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine, and more particularly to an exhaust gas recirculation device for an internal combustion engine provided with a foreign matter collecting filter in an exhaust gas recirculation path.

  Some vehicle engines (internal combustion engines) are equipped with an exhaust gas recirculation device in order to perform exhaust gas recirculation (hereinafter also referred to as EGR (Exhaust Gas Recirculation)) effective in reducing NOx (nitrogen oxides). It is increasing. Also, in contrast to the HPL (High Pressure Loop) -EGR system that recirculates a portion of the hot exhaust gas to the intake side, the exhaust gas after passing through the exhaust turbine and exhaust aftertreatment device of the turbocharger is turbocharged. An LPL (Low Pressure Loop) -EGR type exhaust gas recirculation device has become widespread, which enables a low temperature and large amount of exhaust gas recirculation by recirculation to the upstream side of the compressor of the feeder.

  In this LPL-EGR type exhaust gas recirculation device, foreign matter such as spatter (spatters at the time of welding) and dropping pieces from the exhaust gas purification device may be generated in the exhaust pipe for recirculating the exhaust gas to the intake passage side. In general, a foreign matter collecting filter is provided in the exhaust gas recirculation path so that no foreign matter enters the compressor of the turbocharger and causes damage.

  As an LPL-EGR system equipped with a foreign matter collecting filter, for example, a foreign matter collecting filter folded in a zigzag so as to have a plurality of inclined surfaces inclined with respect to the flow direction of EGR gas and a substantially horizontal plane connecting them. Even if condensate tends to adhere to the inclined surface of the foreign matter collecting filter that is placed in the low-pressure side exhaust recirculation passage of the LPL-EGR circuit and allows the recirculated exhaust gas to pass through, the condensed water easily flows down from the inclined surface. What was made to obtain is known (for example, refer patent document 1).

  In addition, a check valve and a trapper capable of storing condensed water discharged through the check valve are provided in the middle of the discharge passage for discharging condensed water generated in the low pressure side exhaust recirculation passage to the outside. By providing an on-off valve that can selectively introduce supercharging air pressure downstream from the compressor of the machine into the trapper, the on-off valve is opened only when condensed water in the trapper is discharged to the outside. Is known in which the check valve is closed and the condensed water generated in the EGR passage is stably discharged while suppressing the backflow of the condensed water to the EGR passage (for example, Patent Document 2). reference).

  Furthermore, in order to prevent condensed water generated from the recirculated exhaust gas from being cooled by the EGR cooler and contacting the catalyst when the condensed water flows down, the condensed water is prevented from being deteriorated or clogged. There is also known one in which a bypass path is set to bypass the condensed water so as to avoid the catalyst when flowing down (see, for example, Patent Document 3).

  In addition, a main passage and a sub-passage branching from the main passage and joining the main passage again are formed in the compressor casing of the turbocharger, and the adsorbent is disposed so as to capture moisture in the sub-passage, It is known that the adsorbent is dried by evaporating the moisture trapped in the adsorbent with a gas flowing in the sub-passage (see, for example, Patent Document 4).

JP 2010-151091 A JP 2008-280945 A JP 2003-0665162 A JP 2009-264339 A

  However, a conventional exhaust gas recirculation device for an internal combustion engine that makes it easy to flow down the condensed water adhering to the foreign matter collecting filter, or a collector or adsorbent that collects the condensed water downstream from the EGR cooler in the exhaust gas recirculation direction. In this case, the condensed water generated in the vicinity of the EGR cooler during the operation of the engine flows into the exhaust passage side at a time when the EGR valve is closed or when the engine load is reduced, and the DPF (Diesel) arranged on the downstream side of the exhaust passage The main part of the exhaust purification unit, such as a particulate filter) base material, etc., is prone to cracks due to a sudden heat change, and the exhaust purification unit may deteriorate early.

  On the other hand, in the case of setting a flow path for condensed water that bypasses the DPF base material, the above-mentioned problems such as cracks can be prevented, but not only the structure is complicated and the cost is increased, but also part of the recirculated exhaust gas. However, since it bypasses the DPF base material and the like, the performance of the exhaust purification unit could not be sufficiently exhibited.

  Further, when the EGR flow rate control is performed by detecting the differential pressure across the EGR passage with a differential pressure sensor, condensed water adheres to the foreign matter collecting filter to form a water film, and the foreign matter collecting filter forms the exhaust gas recirculation passage. If it is blocked or the pressure loss increases, the EGR flow rate will be erroneously judged to be a large amount of EGR flow (exhaust gas recirculation amount) even though the EGR flow rate is reduced, and the EGR flow rate of the entire system will be insufficient. As a result, the NOx reduction effect may not be sufficiently obtained.

  Furthermore, when an adsorbent that adsorbs condensed water is provided downstream of the EGR cooler in the exhaust gas recirculation direction, if the condensed water adsorbed by the adsorbent is difficult to evaporate, the adsorbent adsorption performance is improved. It could not be maintained, and acidic condensed water could enter the intake pipe, which could easily corrode the turbocharger compressor and the main metal parts of the intake system downstream.

  That is, in the conventional exhaust gas recirculation device for an internal combustion engine, it has been difficult to achieve both prevention of deterioration of main parts due to condensed water and ensuring of exhaust purification performance.

  Therefore, the present invention provides a low-cost exhaust gas recirculation device for an internal combustion engine that can simultaneously prevent deterioration of main parts due to condensed water and ensure exhaust purification performance.

  In order to solve the above problems, an exhaust gas recirculation apparatus for an internal combustion engine according to the present invention is (1) an exhaust gas recirculation apparatus for an internal combustion engine equipped in an internal combustion engine having an exhaust gas purification unit in the middle of an exhaust pipe forming an exhaust gas passage. An exhaust gas recirculation pipe for recirculating the exhaust gas purified by the exhaust gas purification unit from the exhaust gas passage side to the intake air passage side of the internal combustion engine; and the exhaust gas to prevent foreign matter from entering the exhaust gas recirculation pipe A foreign matter collecting filter disposed in the vicinity of the upstream end of the reflux pipe and projecting from the inner wall surface of the exhaust pipe into the exhaust gas passage, and provided in the exhaust gas passage adjacent to the foreign matter collection filter. A water absorbing material.

  In this invention, even if the condensed water in the exhaust gas recirculation pipe flows down to the foreign matter collecting filter side and part of the condensed water adheres to the foreign matter collecting filter without passing through the foreign matter collecting filter, Or heated in high-temperature exhaust gas to evaporate quickly, and the formation of a water film on the foreign matter collecting filter is effectively suppressed. Further, since the water absorbing material is constantly exposed to the high-temperature exhaust gas in the exhaust pipe, evaporation of condensed water from the water absorbing material is promoted, and the water absorbing performance of the water absorbing material is maintained well. Therefore, the passage in the exhaust gas recirculation pipe is surely prevented from being blocked by a foreign matter collecting filter with condensed water attached, and the construction of the apparatus and the high cost can be avoided. It becomes a low-cost exhaust gas recirculation device that can achieve both prevention of exhaust gas and ensuring exhaust gas purification performance. The water-absorbing material referred to here is an exhaust gas passage by separating condensed water from the foreign matter collecting surface portion so as to prevent the condensed water adhering to the foreign matter collecting surface portion of the foreign matter collecting filter from forming a water film. As long as it can be discharged into the inside, the arrangement, material, shape and the like are not particularly limited.

  In the exhaust gas recirculation apparatus for an internal combustion engine according to the present invention, (2) the exhaust gas purification unit has a cylindrical case portion disposed in the middle of the exhaust pipe, and the exhaust gas recirculation pipe is connected to the exhaust gas purification unit. Exhaust gas that has passed through a part is recirculated from the exhaust gas passage side to the intake passage side, and the foreign matter collecting filter is located near the upstream end of the exhaust gas recirculation pipe from the part of the exhaust purification unit. It is preferable that a projecting portion projecting into the exhaust gas passage from the inner wall surface of the cylindrical case portion on the downstream side is provided, and the water absorbing material is held by the projecting portion of the foreign matter collecting filter.

  With this configuration, the foreign matter collecting filter can be exposed to the exhaust gas passing through the cylindrical case portion with a large area, and the gas passage surface (foreign matter capturing portion) intersects the direction of the exhaust gas flow in the cylindrical case portion. (Collecting surface) can be easily formed, and sufficient heat transfer from the cylindrical case portion having a large heat capacity to the foreign matter collecting filter and the water absorbing material becomes possible.

  In the case of having the configuration described in (2) above, (3) an exhaust cooler that cools exhaust gas that is installed in the middle of the exhaust gas recirculation pipe and recirculates to the intake pipe side, and that has an upstream end of the exhaust gas recirculation pipe An outlet portion of the exhaust cooler so that the condensed water generated in the exhaust cooler is discharged into the exhaust gas passage downstream of the part of the exhaust purification unit through the foreign matter collecting filter. It is preferable that it descends toward the inner wall surface side of the cylindrical case part downstream from the part. With this configuration, acidic condensed water generated by cooling the exhaust gas in the exhaust gas recirculation pipe is directed from the inlet portion of the exhaust cooler toward the inner wall surface side of the cylindrical case portion downstream of the exhaust purification unit. As a result, it becomes difficult to flow down and flow into the intake passage side, and the intake system parts are hardly corroded.

  When it has the structure as described in said (2) or (3), it is preferable that (4) the said water absorbing material is located between the said foreign material collection filter and the said one part of the said exhaust gas purification unit. With this configuration, when the condensed water in the exhaust gas recirculation pipe flows down to the foreign matter collecting filter, the condensed water that has passed through the foreign matter collecting filter comes into contact with the part of the exhaust purification unit that becomes high temperature due to the passage of the exhaust gas. Therefore, it is possible to reliably prevent a part of the exhaust purification unit from being cracked or rapidly deteriorated due to a rapid thermal change.

  In the case of having any one of the above configurations (2) to (4), (5) the water absorbing material faces the part of the exhaust gas purification unit on one side and the foreign matter collecting filter on the other side. It is preferable to form an adjacent plate-like body. As a result, the water absorbing material can sufficiently absorb condensed water on the other surface side while sufficiently exposing the water absorbing material to the exhaust gas passing through the exhaust gas passage on the one surface side having a relatively large area and evaporating water.

When having the configuration of (5) above, (6) a blocking portion closed by the water absorbing material at a position where the foreign matter collecting filter is separated from the inner wall surface of the cylindrical case portion into the exhaust gas passage; It is also preferable to have a foreign matter collecting surface portion that has a substantially cylindrical shape between the closed portion and the inner wall surface of the cylindrical case portion. In this case, the foreign matter collecting filter allows the exhaust gas flowing into the exhaust gas recirculation pipe to pass through a wide gas passage area, and the foreign matter collecting area of the foreign matter collecting filter can be sufficiently secured.
In the case of having any one of the constitutions (2) to (6), (7) the part of the exhaust purification unit is an exhaust purification filter part capable of purifying exhaust gas passing through the cylindrical case part. Is preferred. In this case, since the exhaust gas from which the particulate matter and the like have been removed is recirculated to the intake passage side, the particulate matter and the like are prevented from accumulating on the main components of the intake system.

  In the exhaust gas recirculation apparatus for an internal combustion engine according to the present invention, (8) the internal combustion engine includes an exhaust turbine that is rotated by energy of exhaust gas flowing through the exhaust gas passage, and the exhaust turbine connected to the exhaust turbine. A turbocharger having an intake air compressor for compressing the intake air is mounted, and the exhaust gas recirculation pipe is an intake air upstream of the intake air compressor in the intake pipe forming the intake passage of the internal combustion engine. It is preferably connected to a tube. With this configuration, it is possible to effectively suppress the formation of a water film on the foreign matter collecting filter at the inlet portion of the exhaust gas recirculation pipe in the low pressure EGR circuit in which the amount of condensed water generated increases, and the passage in the exhaust gas recirculation pipe is blocked. The required low pressure EGR amount can be secured.

  According to the present invention, even if the condensed water in the exhaust gas recirculation pipe flows down to the foreign matter collecting filter side and part of the condensed water adheres to the foreign matter collecting filter without passing through the foreign matter collecting filter, the condensed water is exhausted. Since it is adsorbed by the water-absorbing material in the gas passage or heated in the high-temperature exhaust gas and rapidly evaporated, it is possible to effectively suppress the formation of a water film on the foreign matter collecting filter. Moreover, by constantly exposing the water absorbing material to the high-temperature exhaust gas in the exhaust pipe, the condensed water from the water absorbing material is accelerated and the water absorbing performance of the water absorbing material is maintained well. It is possible to reliably prevent the passage in the pipe from being blocked by the foreign matter collecting filter to which condensed water adheres, and to avoid the complicated structure and high cost of the apparatus. As a result, it is possible to provide a low-cost exhaust gas recirculation device for an internal combustion engine that can achieve both prevention of deterioration of main parts due to condensed water and ensuring of exhaust purification performance.

1 is an overall schematic configuration diagram of an exhaust gas recirculation device for an internal combustion engine according to an embodiment of the present invention. It is a principal part schematic sectional drawing of the exhaust gas recirculation apparatus of the internal combustion engine which concerns on one Embodiment of this invention. It is a block diagram of the principal part periphery of the exhaust gas recirculation apparatus of the internal combustion engine which concerns on one Embodiment of this invention. 1 is a schematic external perspective view of a foreign matter collecting filter in an exhaust gas recirculation device for an internal combustion engine according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of the attachment portion of the foreign matter collecting filter and the water absorbing material in the exhaust gas recirculation device for an internal combustion engine according to the embodiment of the present invention. It is explanatory drawing of the deformation | transformation aspect of the foreign material collection filter and water absorbing material in the exhaust gas recirculation apparatus of the internal combustion engine which concerns on one Embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(One embodiment)
1 to 5 show an embodiment of an exhaust gas recirculation device for an internal combustion engine according to the present invention.

  In this embodiment, the present invention is applied to an in-line four-cylinder diesel engine 10 (hereinafter simply referred to as the engine 10) which is a multi-cylinder internal combustion engine.

  As shown in FIG. 1, the engine 10 of the present embodiment has a plurality of cylinders 11 in a main body block 10M. The engine 10 includes combustion chambers (details are not shown) in each cylinder 11. A common rail fuel injection device 12 for injecting fuel into the combustion chamber, an intake device 13 for inhaling air into the combustion chamber, an exhaust device 14 for exhausting exhaust gas from the combustion chamber, and exhaust energy in the exhaust device 14 Then, the turbocharger 15 that compresses the intake air in the intake device 13 and supercharges the air into the combustion chamber, and returns a part of the high-pressure side exhaust gas upstream from the turbocharger 15 to the intake side. HPL-EGR device 16 which is a high-pressure side exhaust gas recirculation device to be recirculated and a low-pressure side exhaust gas which recirculates and recirculates a part of the low-pressure side exhaust gas downstream from turbocharger 15 to the intake side. LP as a reflux device And -EGR device 17, is equipped with.

  The fuel injection device 12 includes a supply pump 21 that pumps fuel from a fuel tank (not shown), pressurizes the fuel to a high fuel pressure (fuel pressure), and discharges the fuel, a common rail 22 into which fuel from the supply pump 21 is introduced, and the common rail And a fuel injection valve 23 that injects the fuel supplied through the cylinder 22 into the combustion chamber at a timing and opening degree (duty ratio) corresponding to an injection command signal from an ECU (electronic control unit) (not shown). The supply pump 21 is driven by, for example, the rotational power of the engine 10, and the common rail 22 distributes and supplies the high-pressure fuel supplied from the supply pump 21 to the plurality of fuel injection valves 23 while keeping it even. The fuel injection valve 23 is constituted by a known needle valve, and by controlling the valve opening time by an injection command signal, fuel (for example, light oil) corresponding to the injection command signal is injected into the combustion chamber. Can be supplied.

  The intake device 13 includes an intake manifold 31, an intake pipe 32 upstream of the intake manifold 31, an air cleaner 33 that cleans intake air by a filter at the most upstream portion of the intake pipe 32, and a downstream side of the turbocharger 15. An intercooler 34 that cools the intake air heated by compression / supercharging by the intake air compressor 15a in the intake pipe portion 32b, an air flow meter 35 that detects the intake flow rate of fresh air, and an intake air amount into the engine 10 A throttle valve 36 for adjustment, an intake air temperature sensor 37 for detecting the intake air temperature, and an intake pipe pressure sensor 38 for detecting the boost pressure of the engine 10 near the inlet of the intake manifold 31 are mounted.

  The exhaust device 14 has an exhaust manifold 41, an exhaust pipe 42 downstream from the exhaust manifold 41, and an exhaust throttle that can increase the exhaust temperature during idling or light load and can control the back pressure of the LPL-EGR device 17. A valve 43 and an exhaust aftertreatment device 46 including a known oxidation catalytic converter 44 and a DPF unit 45 mounted on an exhaust pipe 42 downstream of the turbocharger 15 are configured.

  The turbocharger 15 includes an intake air compressor 15a and an exhaust turbine 15b that are integrally coupled to each other in the rotational direction. The intake air compressor 15a is rotated by rotating the exhaust turbine 15b and exhaust air compressor 15a by exhaust energy. The intake air can be compressed by the compressor 15 a to supply positive pressure air into the engine 10.

  The HPL-EGR device 16 is mounted between the HPL-EGR pipe 61 and the HPL-EGR pipe 61 interposed between the exhaust manifold 41 and the intake pipe 32, and adjusts the recirculation amount of the exhaust gas. An HPL-EGR valve 62 that can be used, and an HPL-EGR cooler 63 that can cool the exhaust gas passing through the HPL-EGR pipe 61 on the way. The HPL-EGR pipe 61 bypasses the combustion chamber in the engine 10, and a part of the exhaust passage in the exhaust pipe 42 upstream of the exhaust turbine 15 b (inside the exhaust pipe part 42 a on the upstream side) or the exhaust manifold 41. The high-pressure side exhaust recirculation passage P1 that connects the exhaust passage inside and the portion of the intake passage 32w in the intake pipe 32 downstream of the intake air compressor 15a (inside the intake pipe portion 32b on the downstream side) is formed. It is a side passage forming member. Further, the HPL-EGR valve 62 is in an open state in which the high pressure side exhaust gas recirculation passage P1 is opened, and in a closed state in which the opening of the high pressure side exhaust gas recirculation passage P1 is restricted, for example, the high pressure side exhaust gas recirculation passage P1 is shut off. It is possible to switch to. Although not shown in detail, the HPL-EGR cooler 63 is provided with a cooling water pipe portion that contacts the EGR gas in a case portion that forms a part of the high-pressure side exhaust gas recirculation passage P1, and is used for cooling that is introduced into the cooling water pipe portion. The high-pressure side recirculated exhaust gas can be cooled by heat exchange between the fluid (for example, engine cooling water) and the high-pressure recirculated exhaust gas passing through the case portion. The high-pressure side exhaust gas recirculation passage P <b> 1 forms a main part of the high-pressure side exhaust gas recirculation path in the HPL-EGR device 16.

  The LPL-EGR device 17 is installed in the middle of the LPL-EGR pipe 71 interposed between the exhaust pipe 42 and the intake pipe 32 and adjusts the recirculation amount of the exhaust gas. An LPL-EGR valve 72 that can be used, an LPL-EGR cooler 73 that serves as an exhaust cooler that can cool the exhaust gas that passes through the LPL-EGR pipe 71, and an exhaust passage in the exhaust pipe 42 on the downstream side. Of these, the exhaust throttle valve 43 that can reduce the opening degree so as to reduce the cross-sectional area of the passage in the exhaust passage portion downstream of the DPF unit 45 is provided.

  The LPL-EGR pipe 71 bypasses the combustion chamber in the engine 10, and a portion of the exhaust gas passage 42 w in the exhaust pipe 42 downstream of the exhaust turbine 15 b (inside the exhaust pipe portion 42 b on the downstream side) and the intake air A low-pressure side exhaust recirculation passage P2 (low-pressure side exhaust recirculation path) that communicates with a portion upstream of the intake air compressor 15a (inside the upstream intake pipe portion 32a) in the intake passage 32w in the pipe 32 is formed. The exhaust gas recirculation pipe is configured to recirculate the exhaust gas purified by the oxidation catalyst converter 44 and the DPF unit 45 from the exhaust gas passage 42w side to the intake passage 32w side. The LPL-EGR valve 72 is in an open state in which the low pressure side exhaust gas recirculation passage P2 is opened, and in a closed state in which the opening of the low pressure side exhaust gas recirculation passage P2 is restricted, for example, the low pressure side exhaust gas recirculation passage P2 is shut off. It is possible to switch to. Furthermore, the LPL-EGR cooler 73 includes a case portion 73a that forms part of the low-pressure side exhaust recirculation passage P2, and a cooling water pipe portion 73b that contacts the EGR gas passing through the case portion 73a and forms a cooling fluid passage. And the low-pressure side recirculated exhaust gas by heat exchange between the cooling fluid (for example, engine cooling water) introduced into the cooling water pipe portion 73b and the recirculated exhaust gas passing through the case portion 73a. Can be cooled. The low-pressure side exhaust recirculation passage P2 is a low-pressure in the LPL-EGR device 17 together with a portion of the intake passage 32w in the intake pipe 32 downstream of the connection position j where the LPL-EGR pipe 71 is connected to the intake pipe 32. Side exhaust gas recirculation path.

On the other hand, the oxidation catalyst converter 44 and the DPF unit 45 are disposed in the middle of the exhaust pipe 42 of the engine 10 and serve as an exhaust purification unit that purifies exhaust gas passing through the inside. That is, the oxidation catalytic converter 44 has an oxidation performance that can change, for example, hydrocarbon (HC) and carbon monoxide (CO) into carbon dioxide (CO ₂ ) and water (H ₂ O). The DPF unit 45 has a honeycomb structure made of, for example, porous ceramics. The DPF unit 45 collects particulate matter (PM) contained in the exhaust gas of the engine 10 and burns PM deposited by the collection. The playback process can be performed.

  As shown in FIGS. 2 and 3, the DPF unit 45 is disposed in the middle of the exhaust pipe 42, and has a cylindrical case portion 51 that extends the exhaust gas passage 42 w in a specific passage section, and a specific portion in the cylindrical case portion 51. As a main part for collecting PM in exhaust gas passing through the passage section and purifying exhaust gas, a PM collection filter unit 52 (part of the exhaust purification unit, exhaust purification filter) housed in the cylindrical case part 51 Part).

  The cylindrical case portion 51 of the DPF unit 45 has a passage cross-sectional area on the downstream side of the PM collection filter portion 52 on the downstream side of the PM collection filter portion 52 in the extended specific passage section of the exhaust gas passage 42w. The inner wall surface 51a (inclined inner wall surface) that inclines and intersects with the cylindrical wall surface 51b around the PM collection filter portion 52 in the direction of diameter reduction (direction in which the diameter decreases) is reduced.

  In addition, the inside of the cylindrical case portion 51 on the downstream side of the PM collection filter portion 52 is a downstream portion of a specific passage section of the exhaust gas passage 42 w extended corresponding to the PM collection filter portion 52. An exhaust gas distribution chamber 53 is defined, and an exhaust gas passage portion 42wx downstream of the exhaust gas distribution chamber 53 in the exhaust gas passage 42w is, for example, on the vehicle rear side from the exhaust gas distribution chamber 53 in FIG. While extending to the near side, the low pressure side exhaust recirculation passage P2 is curved while extending from the exhaust gas distribution chamber 53 to the upper side in FIG.

  On the other hand, in the vicinity of the upstream end 71u of the LPL-EGR pipe 71 that forms the low-pressure side exhaust recirculation passage P2, the inside wall surface 51a of the cylindrical case portion 51 that constitutes a part of the exhaust pipe 42 enters the exhaust gas passage 42w. A convex-shaped foreign matter collecting filter 80 is provided.

  The foreign matter collecting filter 80 is formed of a metal mesh (a net made of metal wire, or a porous body having a porosity) that is sufficiently finer than the honeycomb-shaped PM collecting filter portion 52 of the DPF unit 45. In addition, spatter (spattering during welding) existing in the exhaust pipe 42, falling pieces from the PM collection filter 52, or foreign matters moving with the exhaust gas from the upstream side of the PM collection filter 52 are generated. The foreign matter is captured at the time, and such foreign matter is prevented from entering the intake air compressor 15a of the turbocharger 15 and causing damage.

  As shown in FIG. 2, the foreign matter collecting filter 80 is an inner wall surface of the cylindrical case portion 51 on the downstream side of the PM collecting filter portion 52 of the DPF unit 45 in the vicinity of the upstream end portion 71 u of the LPL-EGR pipe 71. 51a protrudes into the exhaust gas distribution chamber 53 which is a part of the exhaust gas passage 42w.

  As shown in FIG. 3, the upstream end 71u of the LPL-EGR pipe 71 includes an annular insertion portion 71i held by an opening peripheral portion 51p formed in the cylindrical case portion 51 of the DPF unit 45, and its annular shape. A flange portion 71f adjacent to the insertion portion 71i and hermetically fixed and held to the cylindrical case portion 51.

  As shown in FIG. 4, the foreign matter collecting filter 80 includes an annular outer peripheral edge 81 sandwiched between an opening peripheral part 51 p of the cylindrical case part 51 and a flange part 71 f of the LPL-EGR pipe 71, and a cylindrical shape. A short cylindrical portion 82 sandwiched between the opening peripheral portion 51p of the case portion 51 and the annular insertion portion 71i of the LPL-EGR pipe 71, and a substantially conical shape protruding from the short cylindrical portion 82 into the exhaust gas passage 42w. And a conical surface filter portion 83 (protrusion portion, foreign matter collecting surface portion) and a substantially disc-shaped tip portion 84 supported by the conical surface filter portion 83.

  At least one of the annular outer peripheral edge portion 81 and the short cylindrical portion 82 is previously welded to the upstream end portion 71u of the LPL-EGR pipe 71, and in this state, the upstream end portion 71u of the LPL-EGR pipe 71 is connected to the DPF unit 45. When being connected to the cylindrical case portion 51, it is held in a sandwiched state as shown in FIGS.

  By the way, in the engine 10 of the present embodiment, the low pressure side exhaust gas recirculation passage P2 formed by the LPL-EGR device 17 with respect to the recirculation exhaust gas in the high pressure side exhaust gas recirculation passage P1 formed by the HPL-EGR device 16. The recirculated exhaust gas in the low-pressure side and the low-temperature side of the recirculated exhaust gas is cooled by the LPL-EGR cooler 73 in the low-pressure side exhaust recirculation passage P2, so that the LPL-EGR Acidic condensed water is easily generated in the cooler 73.

  Therefore, the upstream end 71u of the LPL-EGR pipe 71 passes through the foreign matter collection filter 80 through the foreign matter collection filter 80 and the exhaust gas passage 42w on the downstream side of the PM collection filter 52 of the DPF unit 45 through the LPL-EGR pipe 71. At least vertically in the vertical direction so as to descend from the inlet portion 73e of the LPL-EGR cooler 73 toward the inner wall surface 51a side of the cylindrical case portion 51 downstream of the PM collection filter portion 52 so as to be discharged into the interior. It extends to.

  More specifically, as shown in FIGS. 2 and 3, the upstream end portion 71u of the LPL-EGR pipe 71 is curved from the vicinity of the flange portion 71f toward the upper side in the vertical direction. The remaining part of the LPL-EGR pipe 71 connected to 71u is composed of flange portions at both ends, a plurality of other tubular members 71j, 71k having bellows-like undulations, a part of the LPL-EGR cooler 73, and the like.

  On the other hand, since the foreign matter collecting filter 80 is made of metal and has a fine mesh, a water film is easily attached to the surface of the foreign matter collecting filter 80 due to surface tension.

  Therefore, a substantially disc-shaped or dish-shaped water absorbing material is disposed on the front end side of the foreign matter collecting filter 80 so as to be adjacent to at least one of the conical filter portion 83 and the front end portion 84 in the exhaust gas passage 42w. 86 is arranged.

  The water absorbing material 86 is provided adjacent to the foreign matter collecting filter 80 so as to be exposed to the exhaust gas in the exhaust gas passage 42w. Although a detailed support structure is not shown, the conical surface filter portion 83 and It is held by at least one of the tip portions 84.

  Further, the condensed water generated in the LPL-EGR cooler 73 passes from the upstream end 71u of the LPL-EGR pipe 71 through the foreign matter collecting filter 80 into the exhaust gas passage 42w downstream of the PM collecting filter 52 of the DPF unit 45. When the water absorbent 86 is discharged, the water absorbing material 86 adheres to the conical filter portion 83 and the tip end portion 84 without passing through the foreign matter collecting filter 80, and condensate water that tends to remain on the foreign matter collecting filter 80. It has a function of sucking out to the exhaust gas passage 42w side so as to be separated from the conical surface filter portion 83 and the tip end portion 84, and adsorbing and holding it.

  The water-absorbing material 86 is formed of, for example, a water-absorbing material or a non-water-absorbing material, but formed as a porous body that can exhibit water absorption.

  Of course, the water absorbing material 86 is removed from the conical surface filter portion 83 so as to suppress the condensed water adhering to the conical surface filter portion 83 which is the foreign matter collecting surface portion of the foreign matter collecting filter 80 from forming a water film. As long as the condensed water can be removed and discharged into the exhaust gas passage 42w, its arrangement, material, shape and the like are not particularly limited, but preferably have heat resistance. Further, the water absorbing material 86 preferably has a function of neutralizing acidic condensed water, and may be composed of a plurality of types of materials.

  Further, the water absorbing material 86 is located between the foreign matter collecting filter 80 and the PM collecting filter portion 52 of the DPF unit 45, and this water absorbing material 86 is on the one surface 86a side of the PM collecting of the DPF unit 45. It forms a plate-like body facing the filter portion 52 and adjacent to the conical surface filter portion 83 and the tip end portion 84 of the foreign matter collecting filter 80 on the other surface 86b side.

  As shown in a schematic cross-sectional view in FIG. 5, the tip end portion 84 of the foreign matter collecting filter 80 is closed by a water absorbing material 86 at a position spaced from the inner wall surface of the cylindrical case portion 51 into the exhaust gas passage 42 w. The conical surface filter portion 83 of the foreign matter collecting filter 80 constitutes a foreign matter collecting surface portion having a substantially cylindrical shape between the tip end portion 84 and the inner wall surface 51a of the cylindrical case portion 51. Yes.

  The operation of the engine 10 is controlled by an ECU (electronic control unit) (not shown) based on sensor information of various sensor groups. For example, discharge control of the supply pump 21 (for example, control of the electromagnetic spill valve) ), Fuel injection amount control by the fuel injection valve 23, opening degree control of the throttle valve 36, opening degree (EGR rate) control of the HPL-EGR valve 62 and LPL-EGR valve 72, and opening degree control of the exhaust throttle valve 43 Control and the like are executed. The various sensor groups referred to here include, for example, the known air flow meter 35, intake temperature sensor 37, intake pipe pressure sensor 38, exhaust oxygen concentration sensor 47, exhaust temperature sensors 48a and 48b, exhaust temperature sensor 49, DPF shown in FIG. In addition to the front-rear differential pressure sensor 91, the low pressure EGR differential pressure sensor 92, and the like, there are an accelerator opening sensor, a throttle opening sensor, a crank angle sensor, a water temperature sensor, a vehicle speed sensor, and the like (not shown). Further, instead of the exhaust throttle valve 43 or in combination with the exhaust throttle valve 43, a low pressure EGR intake throttle valve 93 may be provided in the upstream intake pipe portion 32a.

  Next, the operation will be described.

  In the exhaust gas recirculation apparatus of the internal combustion engine of the present embodiment configured as described above, acidic condensed water is generated by cooling the recirculated exhaust gas in the vicinity of the LPL-EGR cooler 73 during the operation of the engine 10. Therefore, when the LPL-EGR valve 72 is closed or the load of the engine 10 is reduced, the condensed water in the LPL-EGR pipe 71 may flow to the exhaust gas passage 42w side at once.

  At this time, the condensed water in the LPL-EGR pipe 71 flows down to the foreign matter collecting filter 80, and a part thereof adheres to the foreign matter collecting filter 80 without passing through the foreign matter collecting filter 80.

  However, the foreign matter collecting filter 80 protrudes from the inner wall surface 51a of the cylindrical case portion 51 into the exhaust gas passage 42w in the vicinity of the upstream end portion 71u of the LPL-EGR pipe 71, and the conical surface filter of the foreign matter collecting filter 80. Since the portion 83 intersects the direction of the exhaust gas flow in the exhaust gas passage 42w, the conical surface filter portion 83 is effectively suppressed from forming a water film. In addition, the foreign matter collecting filter 80 and the water absorbing material 86 are not only constantly exposed to the high-temperature exhaust gas flow passing through the exhaust gas passage 42 w in a relatively wide area, but also from the conical surface filter portion 83 by the water absorbing material 86. Since the condensed water is absorbed so as to be separated, the condensed water adhering to the foreign matter collecting filter 80 is adsorbed by the water absorbing material 86 or heated in the high-temperature exhaust gas and quickly evaporated. Furthermore, since the water adsorbed on the water absorbing material 86 in the high temperature exhaust gas in the exhaust gas passage 42w is efficiently evaporated in the exhaust gas passage 42w, the water absorbing performance of the water absorbing material 86 is maintained well, The conical surface filter portion 83 is more effectively suppressed from forming a water film.

  Therefore, even if the recirculated exhaust gas does not flow in the low pressure side exhaust recirculation passage P2 formed by the LPL-EGR device 17 because the opening of the LPL-EGR valve 72 is small or the flow rate is small, the foreign matter The conical surface filter portion 83 that forms the foreign matter collection surface of the collection filter 80 is less likely to form a water film, and the passage in the LPL-EGR pipe 71 is prevented from being blocked, so that the required low pressure EGR amount is reduced. Will be secured.

  In addition, since the foreign matter collecting filter 80 is always in contact with the cylindrical case portion 51 having a large heat capacity at the annular outer peripheral edge portion 81 and the short tubular portion 82, the foreign matter collecting filter 80 has a large heat capacity. Sufficient heat transfer to the filter 80 and the water absorbing material 86 becomes possible, and even when the recirculated exhaust gas does not flow into the low pressure side exhaust recirculation passage P2, the cylindrical case portion 51 side to the foreign matter collecting filter 80 is provided. In this respect, the foreign matter collecting filter 80 is difficult to form a water film.

  That is, the exhaust gas recirculation passage in the LPL-EGR pipe 71 has a foreign substance to which condensed water adheres by a simple configuration in which the foreign matter collection surface portion of the foreign matter collection filter 80 and the water absorbing material 86 are disposed in the exhaust gas passage 42w. It is possible to reliably prevent clogging by the collection filter 80, avoid the complicated structure and high cost of the exhaust gas recirculation device, and achieve both prevention of deterioration of main parts due to condensed water and ensuring of exhaust purification performance. It is possible to provide a low-cost exhaust gas recirculation device.

  Further, in the present embodiment, the upstream end 71 u side of the LPL-EGR pipe 71 is downstream of the PM collection filter portion 52 of the DPF unit 45 through the foreign matter collection filter 80 for the condensed water generated in the LPL-EGR cooler 73. Since the exhaust gas is cooled in the LPL-EGR pipe 71, the acidic condensate generated by cooling the exhaust gas in the LPL-EGR pipe 71 becomes the inlet portion 73e of the LPL-EGR cooler 73. From the PM collection filter portion 52 of the DPF unit 45 to the downstream side, and more difficult to flow into the intake passage 32w side. Accordingly, the metal parts of the intake system (valves, parts of the intake air compressor 15a, etc.) are not easily corroded.

  Further, since the water absorbing material 86 is located between the foreign matter collecting filter 80 and the PM collecting filter portion 52 of the DPF unit 45, the condensed water directed to the PM collecting filter portion 52 and the flow of the droplets thereof are flown. When the condensed water in the LPL-EGR pipe 71 flows down to the foreign matter collecting filter 80 side, the condensed water that has passed through the foreign matter collecting filter 80 will be blocked by the water absorbing material 86. It is suppressed reliably that it contacts. Therefore, it is possible to reliably prevent the PM collection filter unit 52 from being cracked or rapidly deteriorated due to a rapid thermal change. In addition, since the exhaust gas after passing through the PM trapping filter part 52 recirculates to the intake side, it is possible to reliably prevent particulate matter and the like from accumulating on the main parts of the intake system.

  In addition, in the present embodiment, the foreign matter collecting filter 80 includes a distal end portion 84 that is blocked by the water absorbing material 86 at a position that is separated from the inner wall surface 51a of the cylindrical case portion 51 of the DPF unit 45 into the exhaust gas passage 42w. The foreign matter collecting filter 80 flows into the LPL-EGR pipe 71 because it has the conical surface filter portion 83 having a substantially cylindrical shape between the tip end portion 84 and the inner wall surface 51 a of the cylindrical case portion 51. The recirculated exhaust gas is allowed to pass through a wide gas passage area, and the foreign matter collection area of the foreign matter collection filter 80 can be sufficiently secured.

  Further, the water absorbing material 86 is sufficiently exposed to the high-temperature exhaust gas passing through the exhaust gas passage 42w on one surface side 86a of a relatively large area to evaporate water, and on the other surface 86b side, the foreign matter collecting filter 80 is provided. Since the condensed water adhering to the conical surface filter portion 83 and the tip portion 84 can be efficiently absorbed, formation of a water film in the conical surface filter portion 83 can be reliably prevented while simplifying the water absorbing material 86.

  Thus, in the present embodiment, the condensed water in the LPL-EGR pipe 71 flows down to the foreign matter collecting filter 80 side, and a part of the condensed water flows into the foreign matter collecting filter 80 without passing through the foreign matter collecting filter 80. Even if it adheres, the condensed water is adsorbed by the water absorbing material 86 in the exhaust gas passage 42w or heated in the high temperature exhaust gas so as to evaporate quickly. Can be effectively suppressed, and by constantly exposing the water absorbing material 86 to the high-temperature exhaust gas in the exhaust pipe 42, evaporation of condensed water from the water absorbing material 86 is promoted, and the water absorbing material Since the water absorption performance of 86 is maintained well, the exhaust gas recirculation passage P2 in the LPL-EGR pipe 71 is surely prevented from being blocked by the foreign matter collecting filter 80 to which condensed water adheres. Both can be prevented from being complicated and costly structure of the exhaust gas recirculation device. As a result, it is possible to provide a low-cost exhaust gas recirculation device for an internal combustion engine that can achieve both prevention of deterioration of main parts due to condensed water and ensuring of exhaust purification performance.

  In the above-described embodiment, the substantially disc-shaped water absorbing material 86 has a plate shape substantially orthogonal to the central axis of the conical surface filter portion 83 of the foreign matter collecting filter 80. As illustrated in a), the substantially disc-shaped water absorbing material 86 may be inclined so as to deviate from a position substantially orthogonal to the central axis of the conical surface filter portion 83 of the foreign matter collecting filter 80. In addition, the shape and the like of the water absorbing material 86 can be changed so that the angle and range at which the foreign matter collecting filter 80 intersects the flow of exhaust gas from the upstream side are different from those of the above-described embodiment. It is also possible to strengthen the water film formation suppressing action in the filter 80 or to facilitate the inflow of exhaust gas into the LPL-EGR pipe 71. Further, as shown in FIG. 6B, the water absorbing material 86 may be configured as a flat plate that is not flat depending on the shape of the foreign matter collecting filter 80, or has a plurality of surfaces and inclinations. It may be divided into

  Furthermore, the annular outer peripheral edge 81 of the foreign matter collecting filter 80 may function as a gasket disposed between the cylindrical case 51 of the DPF unit 45 and the flange 71f of the LPL-EGR pipe 71. .

  Needless to say, the shape of the foreign matter collecting filter 80 protruding into the exhaust gas passage 42w is not limited to a substantially conical shape, a hemispherical shape, a substantially truncated cone shape, or the like.

  As described above, in the exhaust gas recirculation device for an internal combustion engine according to the present invention, the condensed water in the exhaust gas recirculation pipe flows down to the foreign material collecting filter, and a part of the condensed water is collected without passing through the foreign material collecting filter. Even if it adheres to the filter, the condensed water is adsorbed by the water-absorbing material in the exhaust gas passage or heated in the high-temperature exhaust gas so that it evaporates quickly. It is possible to effectively suppress the formation, and by constantly exposing the water absorbing material to the high temperature exhaust gas in the exhaust pipe, the evaporation of condensed water from the water absorbing material is promoted, and the water absorbing performance of the water absorbing material is good. Therefore, it is possible to reliably prevent the passage in the exhaust gas recirculation pipe from being blocked by a foreign matter collecting filter with condensed water attached, and to avoid the complexity and cost of the apparatus. You can As a result, there is an effect that it is possible to provide an exhaust gas recirculation device for a low-cost internal combustion engine capable of achieving both prevention of deterioration of main parts due to condensed water and ensuring of exhaust purification performance, and exhaust gas recirculation. This is useful for exhaust gas recirculation devices for internal combustion engines that are provided with a foreign matter collecting filter in the path.

10 engine (diesel engine, internal combustion engine)
15 Turbocharger 15a Intake air compressor 15b Exhaust turbine 16 HPL-EGR device (exhaust gas recirculation device on the high pressure side)
17 LPL-EGR device (exhaust gas recirculation device on the low pressure side)
32 Intake pipe 32w Intake passage 42 Exhaust pipe 42w Exhaust gas passage 43 Exhaust throttle valve 44 Oxidation catalytic converter 45 DPF unit (exhaust purification unit)
51 Cylindrical case part 51a Inner wall surface (inclined inner wall surface)
51b Tubular wall surface (wall surface around the exhaust purification filter section)
51p Opening peripheral part 52 PM collection filter part (a part of exhaust purification unit, exhaust purification filter part)
71 LPL-EGR pipe (exhaust gas recirculation pipe)
71f Flange part 71i Annular insertion part 71u Upstream end part 72 LPL-EGR valve 73 LPL-EGR cooler (exhaust cooler)
73a Case part 73b Cooling water pipe part 73e Inlet part 80 Foreign material collection filter 81 Annular outer peripheral edge part (annular base end part)
82 Short cylinder (annular base end)
83 Conical surface filter part (foreign matter collecting surface part)
84 Tip (projection)
86 Water absorption material P1 High pressure side exhaust recirculation passage P2 Low pressure side exhaust recirculation passage

Claims (8)

An exhaust gas recirculation device for an internal combustion engine equipped in an internal combustion engine having an exhaust purification unit in the middle of an exhaust pipe forming an exhaust gas passage,
An exhaust gas recirculation pipe for recirculating the exhaust gas purified by the exhaust gas purification unit from the exhaust gas passage side to the intake passage side of the internal combustion engine;
A foreign matter collecting filter disposed in the vicinity of the upstream end of the exhaust gas recirculation pipe so as to prevent foreign substances from entering the exhaust gas recirculation pipe, and protruding from the inner wall surface of the exhaust pipe into the exhaust gas passage;
An exhaust gas recirculation device for an internal combustion engine, comprising: a water absorbing material provided adjacent to the foreign matter collecting filter in the exhaust gas passage.   The exhaust purification unit has a cylindrical case portion disposed in the middle of the exhaust pipe, and the exhaust recirculation pipe allows the exhaust gas that has passed through a part of the exhaust purification unit to be taken into the intake gas from the exhaust gas passage side. The exhaust gas passage is circulated from the inner wall surface of the cylindrical case portion downstream of the part of the exhaust purification unit in the vicinity of the upstream end portion of the exhaust gas recirculation pipe. 2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, further comprising a projecting portion projecting inside, wherein the water absorbing material is held by the projecting portion of the foreign matter collecting filter.   An exhaust cooler that cools the exhaust gas that is installed in the middle of the exhaust gas recirculation pipe and cools back to the intake pipe side is provided, and an upstream end of the exhaust gas recirculation pipe supplies the condensed water generated in the exhaust cooler. The inside of the cylindrical case part downstream from the part from the inlet part of the exhaust cooler so as to be discharged into the exhaust gas passage downstream from the part of the exhaust purification unit through a foreign matter collecting filter. The exhaust gas recirculation device for an internal combustion engine according to claim 2, wherein the exhaust gas recirculation device is lowered toward the wall surface.   The exhaust gas recirculation device for an internal combustion engine according to claim 2 or 3, wherein the water absorbing material is located between the foreign matter collecting filter and the part of the exhaust gas purification unit.   The water-absorbing material has a plate-like body that faces the part of the exhaust purification unit on one side and is adjacent to the foreign matter collecting filter on the other side. The exhaust gas recirculation device for an internal combustion engine according to any one of claims 4 to 4.   A closed portion closed by the water-absorbing material at a position where the foreign matter collecting filter is separated from the inner wall surface of the cylindrical case portion into the exhaust gas passage; and the closed portion and the inner wall surface of the cylindrical case portion The exhaust gas recirculation device for an internal combustion engine according to claim 5, further comprising a foreign matter collecting surface portion having a substantially cylindrical shape therebetween.   The claim according to any one of claims 2 to 6, wherein the part of the exhaust purification unit is an exhaust purification filter part capable of purifying exhaust gas passing through the cylindrical case part. An exhaust gas recirculation device for an internal combustion engine as described.   The internal combustion engine includes a turbocharger having an exhaust turbine that is rotated by energy of exhaust gas flowing in the exhaust gas passage, and an intake air compressor that is connected to the exhaust turbine and compresses intake air in the intake passage. The exhaust gas recirculation pipe is mounted and connected to an intake pipe upstream of the intake air compressor in the intake pipe forming the intake passage of the internal combustion engine. The exhaust gas recirculation device for an internal combustion engine according to any one of claims 7 to 10.

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